Learning Objectives
• Innovations in operating systems development
• The basic role of an operating system
• The major operating system software subsystem managers and their functions
• The types of machine hardware on which operating systems run
Understanding Operating Systems, Fifth Edition

Learning Objectives (continued)
• The differences among batch, interactive, real-time, hybrid, and embedded operating systems
• Multiprocessing and its impact on the evolution of operating system software
• Virtualization and core architecture trends in new operating systems
Understanding Operating Systems, Fifth Edition

Introduction
• Operating systems
– Manage computer system hardware and software
• This text explores:
– What they are
– How they work
– What they do
– Why they do it
• This chapter describes:
– How operating systems work
– The evolution of operation systems
Understanding Operating Systems, Fifth Edition

What is an Operating System?
• Computer System
– Software (programs)
– Hardware (physical machine and electronic components)
• Operating System
– Part of computer system (software)
– Manages all hardware and software
• Controls every file, device, section of main memory and nanosecond of processing time
• Controls who can use the system
• Controls how system is used
Understanding Operating Systems, Fifth Edition 5

Operating System Software
• Includes four essential subsystem managers
– Memory Manager
– Processor Manager
– Device Manager
– File Manager
• Network Manager (fifth subsystem manager)
– In all modern operating systems
– Assumes responsibility for networking tasks
– Discussed further in Chapters 9 & 10
Understanding Operating Systems, Fifth Edition 6

Operating System Software
(continued)
• User Command Interface
– Provides user communication
• User issues commands to operating system
– Unique to each operating system
• May vary between versions
– Essential managers provide support
Understanding Operating Systems, Fifth Edition 7

Operating System Software
(continued)
Understanding Operating Systems, Fifth Edition 8

Operating System Software
(continued)
• Each manager:
– Works closely with other managers
– Performs a unique role
• Manager tasks
– Monitor its resources continuously
– Enforce policies determining:
• Who gets what, when, and how much
– Allocate the resource (when appropriate)
– Deallocate the resource (when appropriate)
Understanding Operating Systems, Fifth Edition 9

Operating System Software
(continued)
• Network Manager
– Operating systems with networking capability
– Fifth essential manager
– Convenient way for users to share resources
– Retains user access control
• Resources include:
– Hardware (CPUs, memory areas, printers, tape drives, modems, and disk drives)
– Software (compilers, application programs, and data files)
Understanding Operating Systems, Fifth Edition 10

Operating System Software
(continued)
Understanding Operating Systems, Fifth Edition 11

Main Memory Management
• In charge of main memory
– Random Access Memory (RAM)
• Responsibilities include:
– Preserving space in main memory occupied by operating system
– Checking validity and legality of memory space request
– Setting up memory tracking table
• Tracks usage of memory by sections
• Needed in multiuser environment
– Deallocating memory to reclaim it
Understanding Operating Systems, Fifth Edition 12

Processor Management
• In charge of allocating Central Processing Unit
(CPU)
• Tracks process status
– An instance of program execution
• Two levels of responsibility:
– Handle jobs as they enter the system
• Handled by Job Scheduler
– Manage each process within those jobs
• Handled by Process Scheduler
Understanding Operating Systems, Fifth Edition 13

Device Management
• In charge of monitoring all resources
– Devices, channels, and control units
• Responsibilities include:
– Choosing most efficient resource allocation method
• Printers, ports, disk drives, etc.
• Based on scheduling policy
– Allocating the device
– Starting device operation
– Deallocating the device
Understanding Operating Systems, Fifth Edition 14

File Management
• In charge of tracking every file in the system
– Data files, program files, compilers, application programs
• Responsibilities include:
– Enforcing user/program resource access restrictions
• Uses predetermined access policies
– Controlling user/program modification restrictions
• Read-only, read-write, create, delete
– Allocating resource
• Opening the file
• Deallocating file (by closing it)
Understanding Operating Systems, Fifth Edition 15

Cooperation Issues
• Essential manager
– Perform individual tasks and
– Harmoniously interact with other managers
• Requires incredible precision
– No single manager performs tasks in isolation
– Network manager
• Convenient way to share resources
• Controls user access
Understanding Operating Systems, Fifth Edition 16

Operating System Software
(continued)
Understanding Operating Systems, Fifth Edition 17

A Brief History of Machine Hardware
• Hardware: physical machine and electronic components
– Main memory (RAM)
• Data/Instruction storage and execution
– Input/Output devices (I/O devices)
• All peripheral devices in system
• Printers, disk drives, CD/DVD drives, flash memory, and keyboards
– Central processing unit (CPU)
• Controls interpretation and execution of instructions
• Controls operation of computer system
Understanding Operating Systems, Fifth Edition 18

A Brief History of Machine Hardware
(continued)
Understanding Operating Systems, Fifth Edition 19

A Brief History of Machine Hardware
(continued)
• Computer classification
– By capacity and price (until mid-1970s)
• Mainframe
– Large machine
• Physical size and internal memory capacity
– Classic Example: 1964 IBM 360 model 30
• CPU required 18-square-foot air-conditioned room
• CPU size: 5 feet high x 6 feet wide
• Internal memory: 64K
• Price: $200,000 (1964 dollars)
– Applications limited to large computer centers
Understanding Operating Systems, Fifth Edition 20

A Brief History of Machine Hardware
(continued)
• Minicomputer
– Developed for smaller institutions
– Compared to mainframe
– Smaller in size and memory capacity
• Cheaper
– Example: Digital Equipment Corp. minicomputer
• Price: less than $18,000
– Today
• Known as midrange computers
• Capacity between microcomputers and mainframes
Understanding Operating Systems, Fifth Edition 21

A Brief History of Machine Hardware
(continued)
• Supercomputer
– Massive machine
– Developed for military operations and weather forecasting
– Example: Cray supercomputer
• 6 to 1000 processors
• Performs up to 2.4 trillion floating-point operations per second (teraflops)
– Uses:
• Scientific research
• Customer support/product development
Understanding Operating Systems, Fifth Edition 22

A Brief History of Machine Hardware
(continued)
• Microcomputer
– Developed for single users in the late 1970s
– Example: microcomputers by Tandy Corporation and
Apple Computer, Inc.
• Very little memory (by today’s standards)
• 64K maximum capacity
– Microcomputer’s distinguishing characteristic
• Single-user status
Understanding Operating Systems, Fifth Edition 23

A Brief History of Machine Hardware
(continued)
• Workstations
– Most powerful microcomputers
– Developed for commercial, educational, and government enterprises
– Networked together
– Support engineering and technical users
• Massive mathematical computations
• Computer-aided design (CAD)
– Applications
• Requiring powerful CPUs, large main memory, and extremely high-resolution graphic displays
Understanding Operating Systems, Fifth Edition 24

A Brief History of Machine Hardware
(continued)
• Servers
– Provide specialized services
• To other computers or client/server networks
– Perform critical network task
– Examples:
• Print servers
• Internet servers
• Mail servers
Understanding Operating Systems, Fifth Edition 25

A Brief History of Machine Hardware
(continued)
• Advances in computer technology
– Dramatic changes
• Physical size, cost, and memory capacity
– Networking
• Integral part of modern computer systems
– Mobile society information delivery
• Creating strong market for handheld devices
– New classification
• By processor capacity, not memory capacity
– Moore’s Law
• Computing power rises exponentially
Understanding Operating Systems, Fifth Edition 26

A Brief History of Machine Hardware
(continued)
Understanding Operating Systems, Fifth Edition 27

Types of Operating Systems
• Five categories
– Batch
– Interactive
– Real-time
– Hybrid
– Embedded
• Two distinguishing features
– Response time
– How data enters into the system
Understanding Operating Systems, Fifth Edition 28

Types of Operating Systems
(continued)
• Batch Systems
– Input relied on punched cards or tape
– Efficiency measured in throughput
• Interactive Systems
– Faster turnaround than batch systems
– Slower than real-time systems
– Introduced to provide fast turnaround when debugging programs
– Time-sharing software developed for operating system
Understanding Operating Systems, Fifth Edition 29

Types of Operating Systems
(continued)
• Real-time systems
– Reliability is key
– Fast and time limit sensitive
– Used in time-critical environments
• Space flights, airport traffic control, high-speed aircraft
• Industrial processes
• Sophisticated medical equipment
• Distribution of electricity
• Telephone switching
– Must be 100% responsive, 100% of the time
Understanding Operating Systems, Fifth Edition 30

Types of Operating Systems
(continued)
• Hybrid systems
– Combination of batch and interactive
– Accept and run batch programs in the background
• Interactive load is light
• Embedded systems
– Computers placed inside other products
– Adds features and capabilities
– Operating system requirements
• Perform specific set of programs
• Not interchangeable among systems
• Small kernel and flexible function capabilities
Understanding Operating Systems, Fifth Edition 31

Brief History of Operating Systems
Development
• 1940s: first generation
– Computers based on vacuum tube technology
– No standard operating system software
– Typical program included every instruction needed by the computer to perform the tasks requested
– Poor machine utilization
• CPU processed data and performed calculations for fraction of available time
– Early programs
• Designed to use the resources conservatively
• Understandability is not a priority
Understanding Operating Systems, Fifth Edition 32

Brief History of Operating Systems
Development (continued)
Understanding Operating Systems, Fifth Edition 33

Brief History of Operating Systems
Development (continued)
• 1950s: second generation
– Focused on cost effectiveness
– Computers were expensive
• IBM 7094: $200,000
– Two widely adopted improvements
• Computer operators: humans hired to facilitate machine operation
• Concept of job scheduling: group together programs with similar requirements
– Expensive time lags between CPU and I/O devices
Understanding Operating Systems, Fifth Edition 34

Brief History of Operating Systems
Development (continued)
• 1950s: second generation (continued)
– I/O device speed gradually became faster
• Tape drives, disks, and drums
– Records blocked before retrieval or storage
– Access methods developed
• Added to object code by linkage editor
– Buffer between I/O and CPU introduced
• Reduced speed discrepancy
– Timer interrupts developed
• Allowed job-sharing
Understanding Operating Systems, Fifth Edition 35

Brief History of Operating Systems
Development (continued)
• 1960s: third generation
– Faster CPUs
– Speed caused problems with slower I/O devices
– Multiprogramming
• Allowed loading many programs at one time
– Program scheduling
• Initiated with second-generation systems
• Continues today
– Few advances in data management
– Total operating system customization
• Suit user’s needs
Understanding Operating Systems, Fifth Edition 36

Brief History of Operating Systems
Development (continued)
• 1970s
– Faster CPUs
– Speed caused problems with slower I/O devices
– Main memory physical capacity limitations
• Multiprogramming schemes used to increase CPU
• Virtual memory developed to solve physical limitation
– Database management software
• Became a popular tool
– A number of query systems introduced
– Programs started using English-like words, modular structures, and standard operations
Understanding Operating Systems, Fifth Edition 37

Brief History of Operating Systems
Development (continued)
Understanding Operating Systems, Fifth Edition 38

Brief History of Operating Systems
Development (continued)
• 1980s
– Cost/performance ratio improvement of computer components
– More flexible hardware (firmware)
– Multiprocessing
• Allowed parallel program execution
– Evolution of personal computers
– Evolution of high-speed communications
– Distributed processing and networked systems introduced
Understanding Operating Systems, Fifth Edition 39

Brief History of Operating Systems
Development (continued)
• 1990s
– Demand for Internet capability
• Sparked proliferation of networking capability
• Increased networking
• Increased tighter security demands to protect hardware and software
– Multimedia applications
• Demanding additional power, flexibility, and device compatibility for most operating systems
Understanding Operating Systems, Fifth Edition 40

Brief History of Operating Systems
Development (continued)
Understanding Operating Systems, Fifth Edition 41

Brief History of Operating Systems
Development (continued)
• 2000s
– Primary design features support:
• Multimedia applications
• Internet and Web access
• Client/server computing
– Computer systems requirements
• Increased CPU speed
• High-speed network attachments
• Increased number and variety of storage devices
– Virtualization
• Single server supports different operating systems
Understanding Operating Systems, Fifth Edition 42

Threads
• Multiple actions executing simultaneously
– Heavyweight process (conventional process)
• Owns the resources
• Passive element
– Lightweight process (thread)
• Uses CPU and scheduled for execution
• Active element
– Multithreaded applications programs
• Contain several threads running at one time
• Same or different priorities
• Examples: Web browsers and time-sharing systems
Understanding Operating Systems, Fifth Edition 43

Object-Oriented Design
• Driving force in system architecture improvements
– Kernel (operating system nucleus)
• Resides in memory at all times, performs essential tasks, and protected by hardware
– Kernel reorganization
• Memory resident: process scheduling and memory allocation
• Modules: all other functions
– Advantages
• Modification and customization without disrupting integrity of the remainder of the system
• Software development more productive
Understanding Operating Systems, Fifth Edition 44

Object-Oriented Design (continued)
Understanding Operating Systems, Fifth Edition 45

Summary
• Operating system overview
• Functions of OS
– Manages computer system
• Hardware and software
– Four essential managers
• Work closely with the other managers and perform unique role
– Network Manager
• Operating systems with networking capability
– Essential hardware components
• Memory chips, I/O, storage devices, and CPU
Understanding Operating Systems, Fifth Edition 46

Summary (continued)
• Evolution of OSs
– Run increasingly complex computers
– Run increasingly complex computer systems
– Prior to mid-1970s
• Computers classified by capacity and price
– Dramatic changes over time
• Moore’s Law: computing power rises exponentially
• Physical size, cost, and memory capacity
• Mobile society information delivery
– Creates strong market for handheld devices
– Integral in modern computer systems
Understanding Operating Systems, Fifth Edition 47

Summary (continued)
• Five categories of operating systems
– Batch, interactive, real-time, hybrid, and embedded
• Use of object-oriented design improves the system architecture
• Several ways to perform OS tasks
• Designer determines policies to match system’s environment
• Next:
– Explore details of operating system components
Understanding Operating Systems, Fifth Edition 48